Project Summary My long-term career goal is to improve outcomes of patients with cardiovascular diseases through optimal medication use. My short-term goal is to address the role of patient and system-level factors on the underuse of oral anticoagulation in atrial fibrillation. The proposed training and research program will put me in a strong positon to become an independent investigator and establish my research group at the intersection of cardiovascular pharmacotherapy, pharmacoepidemiology, and health services research. Candidate: My background in pharmacy and health services research has enabled me to lead 16 first-author peer-reviewed manuscripts. However, I lack advanced methodological skills necessary to evaluate how patient and system-level factors affect oral anticoagulation use. The training proposed in this K01 award will build on my on my background and provide me with the skills I currently lack to conduct the proposed research. Training Plan: This plan includes formal coursework, workshops, seminars and personal mentoring. I will dedicate 75% effort to the training and research activities proposed, under the supervision of my primary mentor Dr. Walid Gellad. Dr. Maria Brooks, Dr. Samir Saba, Dr. William Shrank, and Dr. Joshua Thorpe will be my co-mentors, and Dr. Ashley Naimi will serve as advisor. My specific training goals are: 1) To learn and implement advanced methods, including group-based trajectory modeling, causal mediation analysis, and hierarchical models; 2) To learn the use of spatial data analysis and visualization in health services research; 3) To develop an in-depth understanding of pharmacy benefits management and design of provider payment models, and learn how health services research findings are translated into innovative insurance, health services delivery, and provider payment models in the real-world setting; and 4) To improve my grant writing skills and submit an R01 grant application. Research plan: The overarching theme of this K01 research program is to improve clinical outcomes of atrial fibrillation patients through optimal oral anticoagulation use. My specific aims are to: 1) Describe trajectories of oral anticoagulation use in the 12 months after first atrial fibrillation diagnosis and test whether patient characteristics and region affect trajectories; 2) Quantify to what extent the geographic variation in the incidence of ischemic stroke among atrial fibrillation patients is attributable to the geographic variation in oral anticoagulation initiation and adherence; and 3) Evaluate the effect of type of insurance coverage and insurer- provider payment models on the use and adherence to oral anticoagulation therapy. Impact: The results from this research will guide policymakers on the design and implementation of interventions targeted at mitigating oral anticoagulation underuse.